13a ecology
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Transcript of 13a ecology
Lecture 13a:Ecology
Lecture 13a:Ecology
EcologyDefinition: the study of interactions between all of the living and non-living components in an environment
So, discussion of ecology can include
Animals and plants
Soil and water qualities
Climate
Human impacts
Communities
Definition: assemblage of populations of multiple species within a single environment
Ex: Fallen log
Ex: Forest
Fairly broad- can be small or large
Communities
Because the organisms in a community have lived together over a long period of time, opportunity for coevolution
When an evolutionary change in one organism influences an evolutionary change in another organism
Ex: Many flowers and their pollinators
Coevolution
Interactions
Communities do not exist in a vacuum- the organisms interact with each other and with the environment-- this is an ecosystem
Community CompositionSpecies richness: what species make up a community- basically just a list
Diversity: richness plus species distribution and relative abundance within the ecosystem
If different species spread throughout, more diverse than if only one is abundant
Succession
Communities change over time- but can take decades to see the changes
Succession is the process of an ecosystem moving to a climax community after a disturbance
Each particular environment will lead to a stable climax community-a specific assemblage of plants and animals best suited to that environment
Primary Succession
Occurs when ‘new’ land becomes available- starts from bare rock or sand after glacier
retreats, lava flows, etc.
Secondary Succession
Occurs after a disturbance- fire, agriculture, etc- there is already soil
present
Succession
In either case, first species are pioneer species- small, short-lived, and quick to mature (i.e. weeds)
First in primary are lichens and mosses- lichens help break down rocks into soil
Gradually, more equilibrium species move in- both plants and animals
Ecological Niche
Niche: the specific ‘role’ of the organism in the ecosystem, including what it eats, where it lives, when it is active, how it interacts with others
Habitat: the part of the ecosystem that the organism in question lives in
Ex: Ecosystem for hippos is African savanna, habitat is the river and surrounding shorelines
Interactions
Organisms interact with each other constantly, both within and outside of their species
Interactions, called symbiotic relationships, can be either positive or negative for each
CompetitionCompetition can be for food, space, nutrients
Competitive exclusion principle: no two species can occupy the same niche at the same time
Leads to niche specialization, a way to reduce competition where different species use different resources, even though both could potentially use the same one
Competition
Character displacement- organisms that have partitioned resources will evolve to suit their acquired niche, and thus the characteristics in question will become more different over time
Ex: bird beaks in birds that eat different foods
Character displacement
Spoonbill-uses bill like a shovel in sand
Pelican- catches fish under water
Heron- stabs larger fish
Skimmer- uses bottom bill to scoop fish from surface
MutualismA relationship in which both members benefit
Also very important
Ex. plants and pollinators
Ex. lichens (algae and fungus, living together)
Ex. Ants and caterpillars
http://www.youtube.com/watch?v=z3bWqlPLpMg&feature=BF&list=PLD91727B50EF35272&index=2
Predation
When one animal eats another
Parasitism is a form of predation in which the predator lives in or on the prey, called the host
Ex: cheetahs and gazelles
Ex: owls and moles
Ex: hookworm and humans!
Commensalism
Relationship when one organism benefits and the other is neutral
Ex: One animal transports another
Ex: Sea anemones and clown fish
Fish: gets protection from
predatorsAnemone: doesn’t
care
Name That Relationship!
Microhylid frog + tarantula?
Name That Relationship!
Hermit crab + sea anemone
Name That Relationship!
Ants + acacia trees
Name That Relationship!
Cerambycid beetle + pseudoscorpion
Community StabilityReally, communities are fragile, not stable- stability is hard to achieve because of natural disasters, human encroachment, etc.
Keystone species are species that help to stabilize community, other species’ survival can depend on this one species
Frequently not abundant
Ex: grizzly bears
Ex: bats in tropical forests
Keystone Species: Sea OtterSea otters live in kelp forests
Eat lots of sea urchins, keep populations low so urchins don’t eat all the kelp
However, fishermen want to remove otters because they also eat abalone
But, if all otters are gone kelp forest will be gone and abalone will be gone because urchins will eat all the kelp and destroy the ecosystem
Role of OrganismsHow an organism feeds is part of its niche:
Autotrophs: take in inorganic nutrients (CO2, minerals) and outside energy source
Plants, algae
These organisms are producers, because they produce food
Role of OrganismsHeterotrophs: need a source of organic nutrients, release CO2
Called consumers, because they consume food
Four types:
Herbivores: eat plants
Carnivores: eat other animals
Omnivores: eat both plants and animals
Detritivores: decompose wastes and dead material
Energy and Chemical Flow
Solar energy enters ecosystem through plants
Plants convert this into chemical energy via photosynthesis
Chemical energy is used by animals
At each level, some energy is used, some lost as heat
Less energy is available to the next level
Chemical Cycles
Plants use nutrients in the soil to make organic compounds
Animals eat the plants and use those compounds
When animals die or eliminate waste, nutrients are broken down by detritivores and returned to soil, available to plants again
Food Webs and Energy/ Chemical FlowFood webs represent energy flow from Producers to Primary Consumers to Secondary and Tertiary Consumers
Can also be drawn to represent detrital food webs, showing what eats waste
Important to realize where energy is stored- may be in living matter (rainforests) or in dead materials (temperate forests)
Trophic Levels
There are always fewer consumers than there are producers, because energy is always lost as heat and used for cellular respiration and growth in every organism
As a general rule, only 10% of energy in one level is available to the next
Another way to see it
Biomass: it takes 10,000 g of grass to support 10g of snake
Primary ProductivityRate at which producers capture and store energy
Depends on species, temperature, moisture, soil
Highest in tropical environments, lowest at high altitudes, tundra, desert
Think of how this relates to high species richness and diversity in tropical rainforest vs. tundra
Rainforest
Tundra